1. Field of the Invention
The invention relates to heat exchanger devices for cooling fluids used in an engine of a motor vehicle, and more particularly, to a heat exchanger package including a coupled radiator and charge air cooler for an engine of a heavy-duty highway truck or bus.
2. Description of Related Art
Heat exchanger packages comprising a radiator and a charge air cooler, also known as an intercooler, have been used for years in over the road highway trucks and buses and other heavy-duty motor vehicles. The radiators provide cooling for the engine coolant, usually a 50-50 solution of water and anti-freeze. The charge air cooler receives compressed, charge or intake air from the turbo- or super-charger and lowers its temperature before it enters the engine intake manifold, thereby making it denser, improving combustion, raising power output, improving fuel economy and reducing emissions. In order to optimize heat transfer in a given heat exchanger package size, the factors of cooling air flow, heat exchanger core restriction, cooling air flow split and cooling air approach and differential temperature must be balanced.
Numerous configurations of the radiator/charge air cooler heat exchanger package have been disclosed in the prior art. Placing both the radiator and charge air cooler side-by-side, so that the full frontal area of each of the cores are exposed to ambient cooling air, provides the best performance, but requires the largest package frontal area. Limitations in the frontal area of radiator and charge-air cooler heat exchanger packages have been sought in order to accommodate the smaller frontal area of motor vehicles, as a result of improved vehicle aerodynamics. Heat exchanger packages with smaller frontal areas have been disclosed for example in U.S. Pat. No. 4,737,727, U.S. Patent Application Publication No. 2003/0106669, and in U.S. patent application Ser. No. 10/289,513.
In another prior art radiator and charge air cooler heat exchanger package, depicted in FIG. 1, the charge air cooler is split between an upper unit 101 and a lower unit 103, disposed respectively behind and in front of radiator 107 with respect to the direction of air flow 127. Radiator 107 has a conventional downflow-type tube and fin core 117 between upper tank 109a and lower tank 109b. Radiator 107 receives coolant 131 from the engine into upper tank 109a and the cooled engine coolant exits as 133 from the lower portion of lower tank 109b, to be transferred back to the engine. Both charge air cooler units 101, 103 are cross-flow type charge air coolers wherein the compressed charge air is flowed horizontally through the respective tube and fin cores 111, 113. Compressed, heated charge air 121 is first flowed into vertically oriented tank 105a of upper charge air cooler 101, through core 111 in direction 129a, and into vertical tank 105b. In unit 101, the charge air is cooled by air 127 as it exits the upper portion of radiator core 117. Thereafter, the partially cooled compressed charge air 123 is then transferred into vertical tank 105d of lower charge air cooler 103, where it is then flowed in horizontal direction 129b through core 113 and into vertical tank 105c, and thereafter exits 125 and flows to the engine intake manifold. In unit 103, the charge air is cooled by air 127 before it flows through the lower portion of radiator core 117. Notwithstanding its novel design, the heat exchanger package of FIG. 1 did not achieve good performance and did not go into normal production, to the inventor's knowledge. It has now been determined that the performance of heat exchanger package of FIG. 1 suffered in large part due to excessive charge air pressure drop through the two charge air cooler units.
Thus there has been a long-felt need to achieve high performance in cooling both engine coolant and charge air, while observing strict limitations in frontal area of a radiator/charge air cooler heat exchanger package.